Apparatus for coating paper



March 4, 1947.

Y W. H. BARRETT ETAL APPARATUS FOR' COATING PAPER Filed Oct. 2B. 1944 Patented Mig. 4, V1947 APPARATUS FOR COATING PAPER William H. Barrett and Bernard K. Asdell, International Falls, Minn., signora to Minnesota and Ontario Paper Company,l Minneapolis,

' Application october 2s, 1944, serialv No. 560358 This invention relates to the art of coating and generally to the art of coating web material, and has reference more particularly to webs of paper which can be processed in a continuous manner while moving at high rates of speed.

One of the objects of the invention is to provide an apparatus for coating web material by which two coats of uniform and continuous films of s claims (ci. sii-o) coating material may be applied to the same side of the web in a predetermined arrangement for insuring uniform products and large quantity production.

Another object of theinvention is to provide a uniform thickness and a coating of material which is durable and flexiblewhich does not extend substantially into the structure of the paper.

The thickness of the coating on the paper or sheet material is extremely important Iboth to the manufacturer and the user. Where the coating is for moisture proofing purposes, a coating Aof constant thickness will provide a finished web or sheet of known moisture proofness. For the manufacturer a variation of coating thicknesses presents more serious problems. In the first instance, a variation of thickness of the coating varies the drying time oi' the coated sheet. Thus, if the drierV is set to dry the coating of al certain thickness, certain portions of the sheet which are lightly coated might be dried to too great an extent with a bad effect on the finished product. Otherl parts of the coated sheet might bear a coating of excessivel thickness which might not be perfectly dry during the travel of the web or sheet, thus producing la product which is not uniform in grade.

It is often desirable to place acoatingfilm of greater than ten pounds per ream of 25 x 28/500 sheetsl on one side of the sheet of paper.' One of the difficulties in applying such a heavy coating is that the coating tends to crawl or in other words, form an uneven surface. It has been discovered that if the heavy coating is applied in two or more applications, the diillculties of producing an uneven finished surface is avoided.

Other objects and advantages of the present invention will be apparent from the accompanying drawings, and the following detailed description; In the drawing forming a part of the specifica tion, similar reference characters indicate corresponding parts in all the views. Figure 1 is a side elevational View of a coating apparatus for carrying outv the process hereinafter described; Figure 2 is a sectional view with parts broken away of the top doctoring roll; and Figure 3 is a sectional 2 view of the felt with thereon.

Referring to the drawing in detail: I8 indicates a roll of raw stock or paper which is to be coated,

means I2 is for controlling the tension on the paper from the unwinding roll I 0. A motor I3 -for driving the coating apparatus is provided and the motor drives the apparatus through members I4, I5 and I8. The web I1 as it is unwound from'the roll, passes over roll I8 which'is supported by arms I9 and tension is maintained on the rolls -I8 by spring 20. which is attached to,

the frame 23 at 22 and to the arm I9 at 2l. The frame for supporting the coating unit consists of upright member 23, lhorizontal members 24, 25,

28, and 28.

The web of paper after passing over roll I8, passes around roll 29 which is suitably secured in bearings 38. The web of paper then passes between tensioning rolls 3| and 33 which are suitably supported by bearings 32 and 34. The

4web of paper after passing between rolls 3l and 38 pass over roll 35 and then under roll 38. Roll 38 is mounted so that tension is maintained on the paperthrough the medium of arms 81 which are pivoted at point 88. The paper then passes over roll 39 which is mounted in bearings 48.` This roll and its bearings are mounted on member 28 and may be adjusted on frame member 28 to a desired position. Mounted in bearings 4I is roll 42 behind which the paper passes. bearings 4I are suitably supported on the frame member 21 by blocks 43. The paper then comesv into contact with drier drum or backing member 44 which is mounted upon shaft 45. The shaft 45 is suitably supported by upright member 48. Associated with the drier drum is felt 41 which is used for 'the purpose of veliminating drier Wrinkles. The felt 41 leaves the surface of the drier and then passes over roll 48 which is suitably mounted in bearings 49. The paper leaves the drier surface and passses over roll 49a which is suitably mounted on bearings 48a. The felt then travels with the paper over rolls 50 and 52 which rolls are respectively mounted in bearings 5I and a coated sheet of paper The' . which is mounted is connected suitable bearings 6| and then surrounds rolls 62 and 64, back into contact with the drier surface. The rolls 62 and 64 are mounted in bearings 63 and A65 which may be moved along the frame members 25 and 23 so as to vary the contacting of the felt with the drier surface. The paper after passing over the roll 52 passes in contact with roll 86 mountedin suitable bearings 61 and then to the Wind-up stand. The wind-up stand consists of rolls 68 and 69 arranged to be driven at the same speed by belt-like member 10.

The roll 13 indicates the coated paper being wound up. The purpose of the roll 12 is to prevent to an excessive, movement of the roll of paper during a wind up.

The coating unit consists of a fountain 14 in metering roll 15. The roll 15 is' mounted inbearing 16 which is supported by arm 11 which is pivoted at 18 so that vthe hard surfaced metering roll 15 and .the fountain can be moved away from the applicator roll 83. Positioned below the fountain 15 is coating supply tank 19. The coating from the fountain 11 flows over the back of the fountain 14 into the supply tank 19. The supply tank 19 is furnis-ned with a coating material from a suitable source not shown. The coating material is withdrawn from the coating container 19'through pipe 80 by pump 8l and forced through pipe 82 into the fountain near the top thereof. Rotating into one side of the fountain is roll 83 which is mounted on suitable bearings 84. -Positioned above the roll 83 inlsuitable bearings 86 is hard surfaced doctor roll 85. The doctor roll 85 is preferably hard surfaced material such as stainless steel,while the applicator rol'l 83 is preferably of a yieldable material such as rubber. Positioned in contact with the doctor roll is resilient surfaced roll 81 which is mounted in suitable bearings 88. This roll is of similar material to that of roll 83, and transfers one coat of'the coating material to the paper. Positioned above roll 81 is hard surfaced roll 90 for doctoring the surplus coating from the surface of the applicator roll 81. This doctoring roll is wiped clean by a resilient surfaced roll 9| suitably mounted in bearings 92. Bearings 92 are supported by member 93 while roll 81 is supported by arm member 94 and the applicator roll 93 is supported by arm member 95a. The arm 95 is pivotally connected to member 95a which member in turn is pivotally connected at 94a so that the applicator roll and the doctor rolls can be moved toward and from the backing roll or drier surface. The arms 93, 94, and 95 'are pivotally connected to upright member 91 at |00, 99, and 98. The upright member 91 is pivot'- ally connected at |0I so that the coating and doctoring rolls .may be moved (by any desired means not shown) away from and toward the drier or backing member to provide means for varying the pressure between the doctoring rolls and applicator rolls. A member |02 is connected to arm 93 at |03 and to member |05 at |04. An eccentric |06 is positioned in arm 94 and connected to the member |02. The eccentric is provided With a handleV |01 for varying the pressure between the rolls 83,` 85, 81 and 9|. Member |05 to member |02 at |04 and to member 95 to control the amount of coating material on applicator roll 83. An eccentric |06a is connected to the framemember carrying the metering roll 15 through member |02a.. The eccentric |06a has connected therewith handle member |01a. To remove the coating material the doctoring lroll 9|, doctor blade |09 is adjustfrom the surface ofy of coating material is ably positioned against the surface. This doctoiing blade is suitablyv supported by member |08. The surplus coating material removed from the roll 9| is returned through trough and pipe I2 to the coating container 19. A

In operation, the coating material is fed to the fountain 14 near the top thereof, and an excess forced between the applicator roll 83 and the metering roll 15. A predeamount from the applicator roll The coating material the coating material from the said depositing roll termined amount of coating material is left upon the surface of the roll 83 by the metering roll 15. The doctor roll 85 removes ,a predetermined 83 and the remainder of the coating on the applicator roll after it has been smoothed and the surplus removed by roll 85 is applied to the web of paper vwhich is supported by the backing roll 44. The coating material now on the surface of the doctoring roll 85 is transferred to the surface of the applicator roll 81. The coating material on the applicator roll 81 is then smoothed and the surplus removed therefrom by doctor roll 90. removed from the surface of the applicator roll 81 is then transferred to the surface of the web of \paper which is supported by the backing roll 44. The coating material removed by the doctor roll 40 is removed by resilient covered doctor roll 9| and then the doctor blade removes the coating material from the doctor` roll 9| and the coating is returned to the coating container.

The paper to be coated preferably contains a moisture content of not more than about ten percent at the timethe first coat of coating material is applied, and the coating material used preferably should have a solid content of greater than sixty percent. The apparatus hereinbefore described may be used with hot melt coating material, and in such a case the backing member or roll 44 is provided with a cooling medium. Where the coating is of the material-adhesive such as starch clay or similar material, the backing means is heated to dry the coating material applied to the paper.

Another feature of cation of a wet film of coating material over another wet film of coating material. This is termed wet trapping. For the purpose of this application, wet trapping is defined as the application of a wet film of coating material over another wet film. It is possible in this application to wet trap without changing the viscosity of the coating material.

What We claim:

1. An apparatus for coating a sheet or the like surface, comprising a container for a, bath of coating material, a rotatable depositing roll dipi ping into the said bath, a metering roll mounted in the bath at a selected distance from the depositing roll, a doctor roll for removing a portion of and smoothing in substantially even lm the coating material remaining on the said depositing roll, a second depositing roll wiping said doctor rolls periphery to remove substantially all the coating material therefrom, a second doctor roll wiping the periphery of said second depositing roll so as to leave a measured quantity of coating material on said periphery. a roll for removing substantially all the coating material from said second doctor roll, and means for removing the coating material from the roll wiping the second doctor roll.

2. An apparatus for depositing a owable adhesive coating to a sheet or the like surface in a this invention is the applil substantially even smoothnlm, comprising a container for a bath f coating material,` a rotatable depositing roll dipping into the bath of coating material, a metering roll mounted in the bath at a .selected distance from vthe depositing roll, a'

doctor roll for removing the coating material from the said depositing roll and smoothing in a'substantially even nlm the coating material rel 'maining on the said depositing rollJ a second depositing roll wiping said doctor rolls periphery to remove substantially all coating material therefrom, a second doctor roll wiping the periphery of said depositing roll so as to leave a measured quantity of coating material on said periphery, a. roll for removing substantially all thel coating. material from said second doctor roll,

means for removing the coating material from the roll wiping the second doctor roll, and backing means for carrying' the sheet material to v which the coating material is supplied.

applicator roll for removing the coating materialv from the surface of the doctor roll, a second hard surfaced doctor roll for removing a portion of the coating material carried by the second applicator roll, a resilient surfaced roll for removing the coating from the second doctor roll and means for supplying coating material to the fount tain.

4. An apparatus for coating a moving web .of

Y paper, comprising a container fora bath oi' coati ing material, a rotatable applicator roll dipping into the said container, al metering roll mounted in the said container at a selected distance from the applicator roll, a doctor roll for removing a portion of the coating material from said appli\ cator roll, a second applicator roll Wip'ing'sub-- stantially all the coating material from the periphery of the doctor roll, aA second doctor roll for removing a portion of the coating material from the said second applicator roll, means for removing the coating material from said doctor roll, andv means for varying the pressure between the applicator rolls and the doctor rolls.

5. An apparatus for coating a moving webV of paper comprising., a container for a bath of coating material, a rotatable applicator roll dipping into the said container, a metering roll mounted at a selected distance from the applicator roll, a

doctor roll for removing'a portion of the coating material from said applicator roll, a second applicator roll wiping substantially all the coating material from the periphery of the doctor roll, means for removing a portion of the coatingv material from said second applicator roll, and means i for varying the pressure between' the applicator rolls and the doctor rolls.-

WILLIAM H. BARRETT. BERNARD K. ASDELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED s'rA'rEsvk PATENTS Number Name Date 737,826 Carrier Sept. 1, 1903 1,282,564 Gage Oct. 22, 1918 Traquair Dec. 9, 1924 

